CVE-2026-21259
High
Description
Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to elevate privileges locally.
SeverityHigh
CVSS7.8
Exploit probability—
Product
Microsoft Excel
PublishedFeb 10, 2026
First seenFeb 10, 2026
Weakness typeCWE-122CWE-122
How to fix
Update
- microsoft office_online_server16.0.10417.20097 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| microsoft excel | 2016 | — |
| microsoft 365_apps | No range specified | — |
| microsoft office | 2019 | — |
| microsoft office_long_term_servicing_channel | 2021, 2024 | — |
| microsoft office_online_server | v < 16.0.10417.20097 | 16.0.10417.20097 |
Check your version
Choose the product and enter the version you run to see whether it falls in the affected range.
In the Intelligence 360 plan
Attack Surface Management
See the assets tied to your domains, the technologies they run and known vulnerabilities in one list.